Advertisement
Browse Subject Areas
?

Click through the PLOS taxonomy to find articles in your field.

For more information about PLOS Subject Areas, click here.

  • Loading metrics

The relationship between greenspace and the mental wellbeing of adults: A systematic review

  • Victoria Houlden ,

    Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Writing – original draft, Writing – review & editing

    v.houlden@warwick.ac.uk

    Affiliation Warwick Institute for Science of Cities, University of Warwick, Coventry, West Midlands, United Kingdom

  • Scott Weich,

    Roles Conceptualization, Data curation, Investigation, Methodology, Supervision, Writing – original draft, Writing – review & editing

    Affiliation ScHARR, University of Sheffield, Sheffield, South Yorkshire, United Kingdom

  • João Porto de Albuquerque ,

    Contributed equally to this work with: João Porto de Albuquerque, Karen Rees

    Roles Supervision, Writing – review & editing

    Affiliation Centre for Interdisciplinary Methodologies, University of Warwick, Coventry, West Midlands, United Kingdom

  • Stephen Jarvis,

    Roles Supervision, Writing – review & editing

    Affiliation Department of Computer Science, University of Warwick, Coventry, West Midlands, United Kingdom

  • Karen Rees

    Contributed equally to this work with: João Porto de Albuquerque, Karen Rees

    Roles Methodology, Writing – original draft, Writing – review & editing

    Affiliation Warwick Medical School, University of Warwick, Coventry, West Midlands, United Kingdom

The relationship between greenspace and the mental wellbeing of adults: A systematic review

  • Victoria Houlden, 
  • Scott Weich, 
  • João Porto de Albuquerque, 
  • Stephen Jarvis, 
  • Karen Rees
PLOS
x

Abstract

Introduction

The view that interacting with nature enhances mental wellbeing is commonplace, despite a dearth of evidence or even agreed definitions of ‘nature’. The aim of this review was to systematically appraise the evidence for associations between greenspace and mental wellbeing, stratified by the different ways in which greenspace has been conceptualised in quantitative research.

Methods

We undertook a comprehensive database search and thorough screening of articles which included a measure of greenspace and validated mental wellbeing tool, to capture aspects of hedonic and/or eudaimonic wellbeing. Quality and risk of bias in research were assessed to create grades of evidence. We undertook detailed narrative synthesis of the 50 studies which met the review inclusion criteria, as methodological heterogeneity precluded meta-analysis.

Results

Results of a quality assessment and narrative synthesis suggest associations between different greenspace characteristics and mental wellbeing. We identified six ways in which greenspace was conceptualised and measured: (i) amount of local-area greenspace; (ii) greenspace type; (iii) visits to greenspace; (iv) views of greenspace; (v) greenspace accessibility; and (vi) self-reported connection to nature. There was adequate evidence for associations between the amount of local-area greenspace and life satisfaction (hedonic wellbeing), but not personal flourishing (eudaimonic wellbeing). Evidence for associations between mental wellbeing and visits to greenspace, accessibility, and types of greenspace was limited. There was inadequate evidence for associations with views of greenspace and connectedness to nature. Several studies reported variation in associations between greenspace and wellbeing by life course stage, gender, levels of physically activity or attitudes to nature.

Conclusions

Greenspace has positive associations with mental wellbeing (particularly hedonic wellbeing), but the evidence is not currently sufficient or specific enough to guide planning decisions. Further studies are needed, based on dynamic measures of greenspace, reflecting access and uses of greenspace, and measures of both eudaimonic and hedonic mental wellbeing.

Introduction

Background

Urbanisation is increasing at an unprecedented rate, and with over half the world’s population now residing in cities [1], many people may not have access to the green landscapes in which the human species evolved [2, 3]. Greenspace may provide human benefits, such as facilitating exercise, social activities and connecting with nature [4], and it is suggested that urban greenspaces are critical to healthy living, both physically [5, 6] and mentally [7, 8]. There may also be salutogenic effects on mental health and wellbeing, such as increased attention, feelings of happiness and reduced stress [9, 10].

The United Nations Sustainable Development Goals emphasise the importance of greenspace provision “to foster prosperity and quality of life for all” [11]. The World Health Organisation stated that urban greenspaces (including parks, woodlands, and sports facilities) are a “necessary component for delivering healthy, sustainable, liveable conditions” [12], while highlighting the dearth of evidence to support planning advice [12]. In the UK, local authorities are responsible for providing access to the natural environment [13], and guidelines recommend that all residents should live within 300m of at least 2 hectares of greenspace [14, 15], despite limited evidence for the wellbeing benefits of these recommendations.

Measuring greenspace

One of the reasons for this dearth of evidence is the lack of consensus regarding the definition of the terms ‘nature’ and ‘natural’ [10, 16], and features that may appear ‘natural’ are often artificially constructed [8]. Hartig et al. provide the most detailed definition of nature, as the “physical features and processes of nonhuman origin…, the ‘living nature’ of flora and fauna” [8].

Furthermore, ‘nature’ and ‘greenspace’ are often used interchangeably [1721]; ‘greenspace’ is more inclusive, referring to areas of grass, trees or other vegetation [22], and can be used to describe both surrounding greenness in the countryside, and spaces managed or reserved in urban environments [14]. Greenspace was therefore chosen as the focus of this review. We chose not to include studies of water (blue space), as this is generally considered separately to greenspace [5, 2325].

Mental wellbeing and greenspace

Mental wellbeing comprises happiness and life satisfaction (hedonic wellbeing) and fulfilment, functioning and purpose in life (eudaimonic wellbeing) [26, 27]. It is therefore a multi-dimensional measure of positive mental health, reflecting more than an absence of mental distress, in which those with the best mental wellbeing are able to realise their potential, cope well with everyday stressors, and flourish mentally. It is increasingly recognised as an indicator of national prosperity [28], due to its associations with productivity, longevity and societal functioning [2830]. While theories suggest that mental wellbeing may be improved by exposure to greenspace, there is limited evidence for clear benefits; many studies use unvalidated measures or proxies such as mental distress or quality of life [7]. Additionally, measures of nature and greenspace vary widely [8, 12, 22].

Previous reviews have examined the relationship between greenspace (/nature) and general health [7, 8, 12], or mental health [31], although the latter has generally been defined in terms of mental distress, rather than mental wellbeing. While Douglas et al. describe their recent scoping review as focussing on “green space benefits for health and well-being”, they include no studies measuring mental wellbeing per se, but provide further evidence for reduced mental distress in greener neighbourhoods [7]. Similarly, Gascon et al.’s review of “Mental Health Benefits” of long-term greenspace exposure includes some studies of aspects of mental wellbeing, but focusses mainly on measures of mental distress, rather than positive mental health [31]. We therefore believe this is the first review to examine greenspace associations specifically with mental wellbeing, in adults.

The aim of this review was therefore to synthesise quantitative evidence for associations between greenspace and mental wellbeing. We were able to identify varying evidence for associations between different characterisations of greenspace and mental wellbeing, while highlighting key areas for future research, and subsequent implications for policy and practice.

Materials and methods

Search strategy and selection criteria

The review was registered with PROSPERO (available at https://www.crd.york.ac.uk/prospero/, ID: CRD42016041377). We followed guidance from York’s Centre for Research and Dissemination and the Cochrane Handbook for Systematic Reviews [32, 33]. A search strategy was developed with an information specialist, undertaken by one reviewer (VH), supported by a second, independent reviewer (SW). The following databases were searched: Applied Social Sciences Index and Abstracts (ASSIA), American Psychological Association (PsychInfo), National Center for Biotechnology Information (PubMED), Elsevier’s Scopus, and Web of Science (WOS). Common keywords relating to greenspace and mental wellbeing were derived from the literature, refined following a trial search in each database; this created a final set of terms for greenspace (greenspace(s), green space(s), open space(s), green, greener, nature, natural, landscape) and mental wellbeing (wellbeing, well-being, wellbeing, happiness, happy, happier, life satisfaction, satisfaction with life). We restricted searches to studies in English, relating to humans, published after 01/01/1980. Searches were run from 07/07/2016 to 31/01/2018. The full electronic searches are shown in Table 1.

Using the in-built database functions, an auto-search was timed to re-run each query on a weekly basis to detect any further publications within the review duration. All articles recovered from initial searches were recorded in Endnote, and duplicates removed. Titles and Abstracts were screened for potential relevance by two reviewers independently, and full texts of shortlisted studies retrieved for formal inclusion/exclusion. It was agreed that any disputed studies would be cautiously retained for full text evaluation.

Study eligibility criteria

Criteria for inclusion were: (a) Population: adults aged over 16 (or all ages, but not wholly or mainly children); (b) Exposure: any measure of greenspace, defined as areas of grass, trees or other vegetation. Studies measuring personal connectedness to nature were included. As we were interested in all greenspace characteristics, we included both urban and rural studies; (c) Control: Comparators must include a control group which differed in the type/degree of exposure to greenspace, or direct comparison before and after an intervention; (d) Outcome: mental wellbeing, ascertained using a validated measure of hedonic and/or eudaimonic mental wellbeing, or one or more aspects of these (e.g. life satisfaction, happiness, quality of life. The General Health Questionnaire (GHQ) is designed to measure psychological distress, but includes several positive items, and is prevalent in the literature; studies using this outcome were therefore included. Instruments designed to capture only symptoms of mental distress were not included; (e) No study designs were explicitly excluded.

Evaluation of evidence

After identifying eligible papers, one reviewer (VH) evaluated study contents by extracting: authors, publication date, country, study design, age of participants, sample size, greenspace measures, methods, outcomes, confounders, and a results summary, including effect sizes (regression coefficients/risk ratio and confidence interval/standard error).

For quality appraisal, risk of bias was assessed using Cochrane-recommended criteria [32]: the Newcastle-Ottawa Scale (NOS), adapted for longitudinal and cross-sectional studies, alongside the Cochrane Risk of Bias (RoB) tool for controlled studies [34, 35]. The criteria cover potential risk of bias arising from: representativeness of the sample, participant awareness of the intervention, control factors, and selection of reported results.

We used established Quality Assessment thresholds to categorise each article [36]. For those assessed using the Cochrane RoB tool, a Good quality study met all criteria (low RoB), while those of Fair quality had moderate RoB not meeting one criterion; Poor quality studies had high RoB, not meeting multiple criteria. More complex scoring criteria were used for papers analysed using the NOS, across three domains: Selection (representativeness of sample, treatment of non-respondents), Comparability (between exposure groups) and Outcome (assessment, soundness). Good studies scored at least 3 for Selection, 1 for Comparability and 2 for Outcome; Fair studies scored at least 2, 1 and 2, respectively. Poor papers scored 1 or less for each category. A final quality rating was given according to the lowest rating for any category.

Stratification by characterisation of greenspace

We identified six types of study, according to the characterisation of greenspace: (a) amount of local-area greenspace, most commonly the proportion of local areas covered by greenspace; (b) greenspace type; (c) views of greenspace; (d) visits to greenspace; (e) accessibility, in terms of proximity to greenspaces and self-reported ‘access’; and (f) subjective connection to nature.

We conducted a narrative review of evidence, as methodological heterogeneity precluded meta-analysis. Evidence for associations between each type of greenspace characteristic and mental wellbeing was classified according to the consistency, strength and methodological quality of the findings, and study design. Evidence of association was categorised using established guidelines used by other studies in the field [37]: Adequate (most studies, at least one Good quality, reported an association between greenspace and mental wellbeing); Limited (more than one study, at least one Good, reported an association, but with inconsistent findings); Inadequate (associations reported in one or more studies, but none Good quality); and No association (several Good quality studies reported an absence of a statistically significant association between greenspace and mental wellbeing).

Results

Titles and abstracts of 485 records were screened, and 75 chosen for full-text evaluation; 42 were found to be eligible. During this process, 10 additional papers were found via Auto-Searching the databases and recommendations. Therefore, 52 papers were finally included in this review (Fig 1).

Among these, 4 were controlled case studies and a further 6 were longitudinal cohort studies; there was one ecological analysis, 4 uncontrolled case studies, the remaining 37 were cross-sectional surveys. Two studies were international, 31 were restricted to Europe, 15 just in the UK; 5 were based in the USA with another 6 in Canada, 10 in Australia. Analyses were confined to urban areas in 22 cases, 9 included only rural greenspace. Sample size ranged from 25 to 30,900 participants, but was not specified in 3 cases. Age ranges were fairly consistent, covering young adults to past retirement age, although 1 focused on ‘youths’ (aged 16–25), 3 studies recruited university students and two included mainly people aged over 55; however, 11 studies did not specify participants’ age. After quality assessment, the majority of studies (n = 27) were determined to be Good, 13 were Fair, and 12 Poor. For Poor studies, Table 2 provides further justification. For full details of the risk of bias for each study, heat maps are presented in S1 and S2 Tables. Table 3 provides further detail on the typologies of greenspace measures implemented for each study.

Mental wellbeing measures

Only 14 studies were found to measure both hedonic and eudaimonic mental wellbeing, of which the most commonly used measure was the Warwick-Edinburgh Mental Well-Being Scale (WEMWBS) [19, 46, 52, 53, 61, 66]. WEMWBS includes 14 positively worded questions, regarding individual feelings over the past 2 weeks, including “feeling relaxed”, “interested in new things”, and “close to others” [81]; there is also a reduced 7-item version, known as SWEMWBS (Shortened-WEMWBS) [82]. The recent Personal Wellbeing ONS4, applied in to one study [72], measures individuals’ life satisfaction, happiness and anxiety (hedonic wellbeing) and sense of worth (eudaimonic wellbeing) [83].

The remaining 32 studies assessed outcomes considered to be aspects of mental wellbeing, such as quality of life, life satisfaction, and affect, but did not report both hedonic and eudaimonic wellbeing. The WHO-5 Well-Being Index, used in 2 studies [48, 70], asks how frequently individuals have felt “cheerful and in good spirits” and “calm and relaxed”, over the previous 2 weeks, but focusses on hedonic rather than eudaimonic wellbeing [84].

Quality of life was measured in 6 studies, two using the WHOQOL-BREF [65, 75], a 26-item questionnaire covering physical and psychological health, social relationships and personal environment [85]. The SF-36 instrument measures quality of life with 36 physical, emotional and psychological health questions [86], and was used in 4 studies [41, 42, 44, 75]. A brief 12-item version (SF-12) has three subscales: mental health, vitality [18], and emotional-role functioning. The mental component summary (MCS), derived from a subset of emotional problems, wellbeing and social functioning questions, was used in 6 papers [21, 40, 50, 57, 74, 75], asking how often the individual recently felt “full of energy”, “nervous” and “happy” [86].

Single-item Life Satisfaction was used in 6 studies [24, 25, 40, 41, 51, 87]. The Satisfaction With Life Scale (SWLS) was applied to 4 studies [75, 7880], and includes a more thorough 5 life-evaluation questions, which ask how ideal and satisfying the individual’s life is, and if they have “gotten the important things… in life” [88].

Happiness was measured with one question in 4 studies [56, 67, 69, 71]. The Attentional Functioning Index (AFI), which assesses daily functioning, was used in one study [62, 89].

Eight studies reported affect scores [62, 63, 6669, 78, 79], which include positive feelings (happiness, interest), and negative emotions (anger, sadness), using the 20-item Positive and Negative Affect Scale (PANAS) [90]. Similarly, The Profile of Mood States (POMS) asks about experiences of 65 different emotions, including some positive items, such as “lively” and “relaxed” [91], and was used in one study [20]. The General Health Questionnaire (GHQ) was used in 14 studies [5, 17, 19, 2325, 38, 45, 47, 49, 54, 58, 60, 73]. It contains some positively worded items (“In the last 2 weeks I have… been able to concentrate”, “felt I have been playing a useful part” and “feeling reasonably happy”) but was designed and validated as a screening tool for psychiatric disorders, with higher scores indicative of greater distress [92]. Other studies which measured on poor mental health were excluded from this review.

Full details of the included studies are presented in Table 2, which is ordered by greenspace characteristic. Where articles cover multiple characteristics, the study appears under multiple headings.

Greenspace characteristics

Amount of local-area greenspace.

21 studies examined associations between quantities of local-area greenspace and mental wellbeing, 2 of which were longitudinal. Most calculated the proportion of greenspace for each Lower-Layer Super Output Area (LSOA, a geographic area generated for being as consistent in population size as possible, with a minimum population of 1000 and the mean of 1500), Census District (CD), or within a defined radius of residents. Two articles measured greenspace area per capita. Of 15 studies, one was restricted to public greenspace [39], and 14 included only urban areas.

Only four (cross-sectional) studies measured hedonic and eudaimonic mental wellbeing (SWEMWBS and ONS4). No statistically significant association was reported between greenspace and mental wellbeing in three studies [46, 52, 72], although urban residents who reported “sufficient local greenspace” showed significantly higher SWEMWBS scores [52]. However, Wood et al.’s study found that a 1ha increase in park area within a 1.6km walk of an individual’s home showed a 0.070-point increases in SWEMWBS score [53]; this suggests that examining greenspace around individuals, rather than aggregating to local area, may better detect associations.

Five studies, 4 of which were Good quality and based in urban areas, found that life satisfaction was significantly higher in areas with more greenspace [24, 39, 41, 51], albeit with small linear effect sizes of 0.002–0.003 [24, 39]. The study by White et al. included a large sample, over 10,000 individuals, demonstrating a slight but significant association between LSOA greenspace proportions and life satisfaction. Another large study by the same authors found no significant association between mental wellbeing and the amount of rural local-area greenspace [25], suggesting that associations may differ between urban and rural environments.

An ecological analysis of over 172 countries measured the amount of green land cover per km2, adjusted for the nation’s size, finding a significant association with better life satisfaction. Despite the large sample size and strong odds ratios (2.450), the study was of poor methodological quality, due to its ecological design and hence inability to adjust for individual-level confounding [51]. Four studies also found the quantity of urban greenspace was associated with quality of life or mental health, characterised by the SF-36 scale and its sub-components [4143, 74]; however, three others, which included only public urban greenspace, found no association [39, 44, 50]. Taylor et al. observed mixed results: the amount of urban greenspace was positively and significantly associated with hedonic wellbeing for two cities in Australia, but not two others in New Zealand [48].

Based on these Good quality studies, we conclude that there is adequate evidence for an association between local-area urban greenspace and life satisfaction, but not rural greenspace. Mixed results provide inadequate evidence for associations with quality of life, mental health, and multi-dimensional mental wellbeing.

GHQ was the outcome in 8 studies, of which 6 were Good quality and 3 were confined to urban areas. All but one [45] found an inverse association between the amount of greenspace and GHQ score [5, 17, 2325, 47, 49, 50], implying reduced mental distress; again, linear regression coefficients varied considerably, from 0.003 to 0.431. The Fair quality study by Dzhambov et al., however, found no statistically significant association for objective greenspace quantities, but observed significantly lower GHQ scores for those with higher perceived greenness in their neighbourhood [45]. In a longitudinal study, Alcock et al. found that people moving to areas with higher greenspace proportions had significantly lower GHQ score after relocating, averaging 0.430 points lower 3 years post-move [23]. Therefore, there was adequate evidence for the inverse association between the amount of local-area greenspace and (lower) GHQ score.

Greenspace types.

A total of 8 Good and 2 Fair quality studies classified greenspace according to greenspace types, using bespoke classification systems; no consensus was observed regarding greenspace typology. Four of these were longitudinal studies.

Only one Fair study measured hedonic and eudaimonic wellbeing, with WEMWBS, comparing linear associations between the amount of sport, recreational and ‘natural’ spaces within a 1.6km buffer of the individual [53]. The strongest associations were observed for sports (0.430 increase in WEMWBS for each additional space), followed by recreational and natural spaces (0.110 each).

One research group conducted four studies (3 longitudinal) using the longitudinal Swedish Health Survey (SHS), based in suburban and rural areas. They classified public greenspace within 300m of each residents’ home into 5 aspects: Serene (quiet, audible ‘nature’), Wild (undeveloped, no visible human impact), Lush (biodiversity), Spacious (large cohesive area) and Cultural (cultural heritage, old trees) [18, 54, 58]. Two studies measured GHQ: the first found associations between Serene or Spacious greenspace and slightly, but significantly, lower GHQ scores for physically active individuals; however, associations with Spacious greenspace held only for women [54]. In the second, only women moving to areas with Serene greenspace had significantly lowered GHQ scores, but with much higher odds than in Annerstedt et al.’s work [58]. In a cross-sectional analysis, these authors found that the total number of green aspects (Serene, Wild, Lush, Spacious, Cultural) was associated with slightly better SF-36 Vitality scores for women [18]. The third longitudinal study found marginally but significantly lower GHQ scores for greater numbers of different green aspects, including those moving between areas [60].

In a cross-sectional study, based on 12,697 observations from 2,020 residents of rural England, no association was found between LSOA land cover classes and GHQ scores. However, individuals who relocated to areas with more arable, grass, ‘natural’, mountainous and heath land had significantly lower GHQ scores post-move [38].

Among 3 cross-sectional studies, urban residents with higher amounts of local vegetative or ‘natural’ greenspaces reported better mental wellbeing: vegetation density and cover, from field surveys and satellite imagery in Australia, were strongly and significantly associated with life satisfaction [55]. The number of trees, or an indicator of how ‘green’ the neighbourhood is, were significantly associated with better mental health (SF-36 Mental Component) and life satisfaction [57, 59]. Residents’ ratings of the ‘quality of their local natural environment’, on a scale of 0–10 (very dissatisfied to very satisfied), was associated with higher SF-36 Mental Component Summary scores [59].

A large cross-sectional study in the UK used app data on users’ self-reported feelings, while their phones’ GPS linked their location to a land-cover database; this novel study therefore benefits from measuring happiness in situ. Being in mountainous, woodland or ‘semi-natural grassland’ areas, as opposed to urban, was associated with approximately 2-points higher happiness, on a scale of 0–10, although no additional factors were controlled for [56].

While most of these studies were Good quality, interpretation is difficult due to lack of consensus in greenspace classification; in addition, four reports were based on data from the same survey. All but one were restricted to either urban or rural areas, so comparisons between these environments is not possible; however, larger effect sizes were observed in rural studies. Two of the Swedish studies concluded that green aspects were associated with lower GHQ scores for women, while 6 others highlighted that Serene (quiet, ‘natural’) and ‘natural’ rural greenspaces were associated with improved life satisfaction, SF-36 and lower GHQ scores, although none defined the term ‘natural’. Additionally, two studies reported an association between subjective perceptions of local greenspace and mental wellbeing. Evidence is therefore limited.

Visits to greenspace.

Seventeen papers reported studies of visits, either comparing mental wellbeing scores before and after an intervention (n = 7), or testing cross-sectional associations with greenspace visiting patterns (n = 10).

Fair quality studies compared happiness and positive affect for those walking in ‘natural’ versus indoor environments [69], and walks in urban versus green areas [66]. The former reported a statistically significant difference in favour of greenspace walking, the latter did not. In a further Fair quality cross-sectional study, Marselle et al. reported a positive association between perceived restorativeness of the walking environment and positive affect and happiness [67].

Duvall and Kaplan observed 73 individuals on a wilderness expedition; attention and affect were improved post-expedition, persisting for 3–4 weeks [62]. Although effects were quite large (score changes of 0.270 to 0.340), participants were not blind to the intervention. A Fair quality uncontrolled study encouraged individuals to engage with ‘nature’ for 30 days by noticing/protecting wildlife, sharing experiences, or connecting with ‘nature’. Participants reported greater happiness following the programme [71]. Similarly, Molsher and Townsend noted mental wellbeing improvements following engagement with environmental volunteering projects [68], although their study displayed high risk of bias. Jakubec, however, reported no association between visiting greenspaces and Quality of Life Inventory score, in a Poor quality study [64].

A further 10 cross-sectional studies of varying quality examined self-reported greenspace visit frequency. Three studies measured both hedonic and eudaimonic wellbeing, with mixed findings [61, 63, 72]. In the first Fair study, university students who claimed greater typical contact with nature reported better mental wellbeing using Ryff’s Scale of Psychological Wellbeing [63, 93]. These findings were not replicated in a Good study by Glichrist et al., who examined associations between mental wellbeing (SWEMWBS) and greenspaces surrounding workplaces in Scotland [61]. White et al.’s Good study, measuring ONS4, found that those spending time outdoors and in nature every day, compared to never, had strong odds (OR 1.960) of a high sense of worth, the effect size decreasing with visit frequency. No associations were detected for visit frequency and hedonic wellbeing, although those reporting visiting greenspace the previous day had higher happiness scores, with no associations for life satisfaction, anxiety or worth [72].

A further 5 studies, one of which was Poor, showed that quality of life and mental health were improved, and GHQ scores reduced, with the number of greenspace visits [19, 21, 50, 52, 65]; Triguero-Mas et al. also noted that associations with mental health were stronger for males than females [50] In a Good study, Mitchell found that those who more regularly visited a local park had lower GHQ scores [19]. However, although Panno et al. observed that greater frequency of greenspace visits was associated with higher hedonic wellbeing, these results were not statistically significant [70], and Dzhambov et al. found no association between time spent in greenspace and GHQ [45].

Due to the mixed quality and inconsistent results, evidence for an association between greenspace visit frequency and mental wellbeing is considered limited.

Views of greenspace.

Association between views of greenspace and mental wellbeing was reported in 3 papers. Gilchrist et al.’s Good quality study found that workers’ satisfaction with their office views, particularly of trees, lawns and flowering plants, was associated with improved mental wellbeing (SWEMWBS) scores [61]. Similarly, urban residents reporting greater visibility of trees from their home had slightly better life satisfaction [59]. Pretty et al. observed increases in self-esteem for those viewing rural pleasant scenes, while both unpleasant urban and rural scenes could be detrimental; however, they did not control for potentially confounding factors [20]. The mixed quality and small study sample leads us to classify the evidence here as inadequate.

Greenspace accessibility.

We identified 8 cross-sectional studies, mostly Good quality, which tested associations between greenspace accessibility and mental wellbeing. Two studies measured mental health using the SF-12 Mental Component, with significant positive findings [57, 74]. In the first, a weak association was found with Euclidean (direct) distance from homes to the nearest public greenspace [74]. In the second, Sugiyama et al. used the Neighbourhood Environment Walkability Scale, which measures self-reported greenspace access. Access to the highest of levels of greenspace (perceived neighbourhood greenness, terciles) was associated with strong odds (OR 1.270) of better mental health [57].

Only one, Fair study compared public greenspace within different Euclidean buffers around individuals’ postcodes [49]. Triguero-Mas et al. found greater amounts of greenspace within 300m were significantly associated with reduced risk of high GHQ scores (dichotomised around 3), with consistent results for control buffers of 100m, 500m, and 1km [49]. Bos et al. found that greenspace within 3km, but not 1km, of homes was significantly associated with greater quality of life [43], although this study was rated as Poor study because of limited statistical reporting. In a larger study, scores on the SF-36 Vitality scale were associated with rural greenspace, but this was only significant for women and within 300m (but not 100m), of their home [18]. Maas et al.’s large cross-sectional study showed that those with more greenspace within 1km, but not 3km, had slightly lower GHQ scores, contrary to findings by Bos et al. [43, 47]. Dadvand et al. also measured GHQ (dichotomised around 3), finding strong odds of low GHQ scores for the amount of greenspace within 100m of homes (OR 1.320), effect sizes reducing with distance (OR 1.250 for 250m, 1.170 for 500m); stronger associations were also noted for subjective, than objective, proximity to greenspace, measured as self-report and calculated presence of a greenspace within a 10-minute walk [73]. Dzhambov et al. also found a significant association between subjective accessibility (time to walk to nearest greenspace) and lower GHQ, although associations for objectively measured Euclidean distance were not statistically significant [45].

Although several of these studies reported an association between greenspace accessibility and aspects of mental wellbeing, different measures of both were used and findings were inconsistent, providing limited evidence of an association.

Subjective connectedness to nature.

We identified 7 cross-sectional studies examining associations between subjective connection to nature and mental wellbeing. The Connectedness to Nature Scale measures the extent to which individuals ‘feel nature is part of their identity’, with particular emphasis on sense of care for nature; this has been linked to the theory of biophilia: that humans possess an innate desire to affiliate with other forms of life [3, 69]. Of these studies, 5 were of Poor quality, with no controls for potential confounding. Four studies demonstrated that self-reported ‘connection to nature’ was positively associated with mental wellbeing [7679]. Effect sizes were moderate and consistent across the studies, although lower methodological quality means their results have limited generalisability; only one was of Good quality, and adjusted for potentially confounding factors. Similarly, meaning in life, quality of life, happiness and affect were higher for those who reported greater connection to nature [65, 75, 76, 79]. Life satisfaction was also positively related to nature connectedness in two studies [79, 80], with moderate effect sizes, although Zhang et al. revealed that the association only held for those who actively engaged with nature [80]. While consistent in their findings, poor study quality means that the evidence is inadequate.

Discussion

Summary of findings

While both the World Health Organisation and United Nations agree that greenspace is vital for healthy, liveable environments [11, 12], it remains unclear which amounts, types and uses of greenspace are most beneficial to mental wellbeing. Previous reviews have focussed on associations between greenspace (or nature) and general health or mental distress [7, 8, 12, 31], but we are not aware of any previous systematic reviews of published evidence specifically for associations between greenspace and validated, positive measures of mental wellbeing in adults. Even after stratifying our review according to the six main ways in which greenspace was conceptualised and measured, methodological heterogeneity precluded meta-analysis. We therefore undertook a narrative synthesis.

The largest number of studies were concerned with the amount of local-area greenspace, although few used detailed hedonic and eudaimonic wellbeing measures. Consistent results revealed adequate evidence for an association between urban local-area greenspace and life satisfaction. This result did not hold for rural greenspace, however. There was also adequate evidence for an association between local-area greenspace and lower GHQ scores.

Inconsistencies in the categorisation of greenspace types, and dearth of definitions, made it difficult to synthesise results; limited evidence was therefore found for associations between mental wellbeing and variety and ‘nature’ in land cover. Evidence was similarly limited for greenspace accessibility, with results generally concluding that nearer greenspace has the strongest associations, but with results differing according to the mental wellbeing measure; limited evidence was also found for associations between greenspace visits and mental wellbeing.

However, while there was some evidence for an association between mental wellbeing and views of greenery and connectedness to nature, this was considered inadequate, due to the mixed quality and small sample sizes of studies. Table 4 provides full details of the evidence summary and implications for research and policy.

Mental wellbeing measures

Only 14 of the 52 studies used a measure of mental wellbeing that captured both hedonic and eudaimonic dimensions, while others measured aspects such as life satisfaction, happiness and quality of life. GHQ, which was designed as a psychiatric screening tool, was included as a prevalent surrogate in the literature, which includes some positive items. Papers using other psychiatric screening tools were excluded if they covered only symptoms, ie mental distress.

Greenspace definitions and indicators

We identified 6 types of assessment in greenspace studies: amount of local-area greenspace, greenspace types, visits to greenspace, views of greenspace, greenspace accessibility and self-reported connection to nature.

The amount of local-area greenspace was most commonly measured as the proportion of greenspace in a resident’s local area, or more specifically within a set radius of participants’ homes. Most of these studies were restricted to urban areas. Most researchers quantified greenspace objectively, while a small number of studies reported associations with perceptions of the adequacy of the amount of local greenspace provision. All studies used either linear or logistic regression, which may overestimate associations in spatial data. Although a number of studies examined different types of greenspace, no consensus was observed for a typology, and as such conflicting results were observed.

One of the UN’s Sustainable Development Goals is to “provide universal access to…green and public spaces” [11]; most studies assessed accessibility by distance to greenspace. While the EU and UK recommend that individuals should have access to a greenspace within 300m of their home [14, 94], only one study conducted sensitivity analysis to test this guideline [49]; no difference in associations was observed for buffers of 100m, 300m, 500m and 1km. One study used buffer radii of 100m and 300m, reporting a significant association between the latter and mental wellbeing, while a second found that associations with GHQ decreased with distance, at 100m, 250m and 500m buffers. Others found contradictory results using radii of 1 and 3km. Another drawback was the use of Euclidean distance, which doesn’t account for access routes. Application of network distance and consideration of pedestrian routes may give a greater indication of accessibility on foot.

Greenspace visiting patterns were measured inconsistently, in small or cross-sectional studies. Individuals who visited greenspace more often reported greater mental wellbeing, though a second study found this held only for eudaimonic wellbeing; no associations were found in an analysis of greenspace adjacent to workplaces. This study did however report a positive association with views of greenspace from the workplace. This is in keeping with previous research showing that green views reduce the effects of stress [810, 95]. While two studies highlighted that the perceptions of greenspace quality were more strongly associated with mental wellbeing than quantity [52, 59], the size of this difference was not estimated.

Individual connection to nature, assessed in seven studies, relied on self-report for both the greenspace and wellbeing measures, thereby carrying a high risk of reporting bias, especially since few controlled for potentially confounding factors.

Strengths and limitations

We conducted a comprehensive database search, thorough screening of articles, risk of bias assessment, and detailed narrative synthesis of the 50 studies which met our inclusion criteria. We identified six different ways in which greenspace was conceptualised and measured, and by which we stratified our review. We believe this is the first review to systematically appraise the evidence for associations between greenspace and adult mental wellbeing, using only validated measures of positive mental health.

Selection criteria were designed to ensure results of sufficient quality and relevance, and we consulted an information specialist to maximise search efficiency. Screening was undertaken by two independent reviewers, to minimise potential bias. While our criteria were designed to be inclusive, an element of subjectivity means there was a possible risk of excluding potentially interesting studies; we attempted to minimise this by appraising each study with assessments recommended by the Cochrane Handbook, which provides guidance for internationally recognised highest-standard research [32, 3437].

We considered all greenspaces, not restricting our criteria to studies specifically in urban areas, although some studies were confined to urban or rural locations. Nationwide studies were likely to have included both, without stratifying for setting. It was difficult, therefore, to draw clear conclusions about interactions between urban and rural location and associations with mental wellbeing. Although there is interest in understanding how urban greenspaces should best be designed and constructed, it was not possible to draw conclusions specifically for those living in cities.

Only one-quarter of included studies measured both hedonic and eudaimonic mental wellbeing; the majority focused only on aspects such as life satisfaction, affect and vitality, while others used measures (such as the GHQ) which combined positive and negative (distress) items.

While several studies implied that ‘nature’ was associated with aspects of mental wellbeing, none provided a definition of this term. To further complicate matters ‘nature’ and ‘greenspace’ were sometimes used synonymously [1719, 21, 72]. Vegetative or ‘natural’ greenspaces, such as those described as ‘serene’ (quiet, ‘natural’), or with more trees, were most strongly associated with aspects of mental wellbeing, although one study found a stronger association for sports facilities. However, there were few direct comparisons between greenspace types. While Government Guidance provides a standardised greenspace typology for urban planning in the UK [15], no studies used this classification.

Studies that considered greenspace accessibility were limited to estimates of Euclidean distances from home rather than access routes [96]. These studies did not take account of participants’ routines, or where they spent their time. None of the included studies assessed greenspace quality (such as captured by the Green Flag Award [97], or the social contexts in which greenspaces are situated [7, 98].

Only 6 out of 50 papers reported longitudinal studies. Cross-sectional analyses cannot distinguish between reverse causality and associations which may be causal in nature, and, like all observational studies, are prone to confounding (especially by indication) and bias. Although 26 studies were deemed to be of Good quality, 12 were Fair, and the remaining 12 were Poor; this was mostly due to lack of control for potentially confounding, minimal statistical reporting, and, in 3 cases, lack of participant blinding to an intervention.

Conclusions

We sought to synthesis and appraise the evidence for associations between greenspace and mental wellbeing, but found few studies measuring both hedonic and eudaimonic wellbeing. Results suggest associations between greenspace and mental wellbeing, particularly hedonic wellbeing. We discovered adequate evidence for associations between urban greenspace and life satisfaction; however, the evidence for the remainder of the greenspace characteristics, including greenspace (land use) type, accessibility, viewing and visiting patterns, was limited or inadequate. Although not a true measure of mental wellbeing, studies using the GHQ were prevalent in the literature. This measure includes some positive items, and we further concluded that there was adequate evidence for associations between greenspace and lower GHQ scores. While our review was limited by the lack of available data to conduct a meta-analysis, we were able to highlight key areas for future research through our narrative synthesis.

Government guidelines for greenspace provision require robust evidence, but evidence is currently not sufficient for informed, specific planning recommendations. Further methodological work in this field is needed, including the development of operational definitions of ‘nature’ and ‘natural’, and agreement on a land use typology. Measures of greenspace quality are also needed. More studies are required to measure both hedonic and eudaimonic mental wellbeing. Greenspace accessibility should also be measured more specifically, using individual travel distances, using spatial methods of analysis, to better understand how greenspaces should be designed and incorporated into environments. Further research is needed that considers differences in associations between greenspace and mental wellbeing in urban versus rural settings.

Supporting information

S1 Table. Heatmap of risk of bias for studies evaluated using the Newcastle-Ottawa Scale adapted for cross-sectional studies.

https://doi.org/10.1371/journal.pone.0203000.s001

(DOCX)

S2 Table. Heatmap of risk of bias for studies evaluated using the Cochrane RoB 2.0 tool.

https://doi.org/10.1371/journal.pone.0203000.s002

(DOCX)

Acknowledgments

We thank Sam Johnson for her guidance on database search strategy.

References

  1. 1. United Nations. World Urbanization Prospects 2014: Highlights. United Nations Publications. 2014.
  2. 2. Wilson EO. Biophilia: Harvard University Press; 1984.
  3. 3. Wilson EO. Biophilia and the conservation ethic. Evolutionary perspectives on environmental problems. 2007:249–57.
  4. 4. Lachowycz K, Jones AP. Towards a better understanding of the relationship between greenspace and health: development of a theoretical framework. Landscape and Urban Planning. 2013;118:62–9.
  5. 5. De Vries S, Verheij RA, Groenewegen PP, Spreeuwenberg P. Natural environments—healthy environments? An exploratory analysis of the relationship between greenspace and health. Environment and planning A. 2003;35(10):1717–31.
  6. 6. Maas J, Verheij RA, Groenewegen PP, De Vries S, Spreeuwenberg P. Green space, urbanity, and health: how strong is the relation? Journal of epidemiology and community health. 2006;60(7):587–92. pmid:16790830
  7. 7. Douglas OL, Mike ; Scott Mark;. Green space benefits for health and well-being: A life-sourse approach for urban planning, design and management. Cities. 2017;66:53–62.
  8. 8. Hartig T, Mitchell R, De Vries S, Frumkin H. Nature and health. Annual review of public health. 2014;35:207–28. pmid:24387090
  9. 9. Kaplan R. Impact of urban nature: A theoretical analysis. Urban ecology. 1984;8(3):189–97.
  10. 10. Ulrich RS, Simons RF, Losito BD, Fiorito E, Miles MA, Zelson M. Stress recovery during exposure to natural and urban environments. Journal of environmental psychology. 1991;11(3):201–30.
  11. 11. United Nations General Assembly. New Urban Agenda2017. http://habitat3.org/the-new-urban-agenda.
  12. 12. World Health Organisation. Urban green spaces and health—a review of evidence. 2016.
  13. 13. Local Government Association. Being Mindful of Mental Health- The role of local government in mental health and wellbeing. Online: 2017 29 Jun 2017. Report No.
  14. 14. Natural England. Nature nearby: accessible natural greenspace guidance. Natural England: Peterborough. 2010.
  15. 15. Planning Policy Guidance. 17: Planning for open space, sport and recreation. Office of the Deputy Prime Minister, London[online] < www communities gov-uk/planningandbuilding/planningsystem/planningpolicy/planningpolicystatements/>[Accessed 1502 11]. 2002.
  16. 16. HM Government. The Natural Choice: Securing the value of nature. Natural Environment White Paper; 2011.
  17. 17. Astell-Burt T, Mitchell R, Hartig T. The association between green space and mental health varies across the lifecourse. A longitudinal study. Journal of epidemiology and community health. 2014;68(6):578–83. Epub 2014/03/08. pmid:24604596.
  18. 18. Bjork J, Albin M, Grahn P, Jacobsson H, Ardo J, Wadbro J, et al. Recreational values of the natural environment in relation to neighbourhood satisfaction, physical activity, obesity and wellbeing. Journal of Epidemiology and Community Health. 2008;62(4).
  19. 19. Mitchell R. Is physical activity in natural environments better for mental health than physical activity in other environments? Social Science & Medicine. 2013;91:130–4. http://dx.doi.org/10.1016/j.socscimed.2012.04.012.
  20. 20. Pretty J, Peacock J, Sellens M, Griffin M. The mental and physical health outcomes of green exercise. International journal of environmental health research. 2005;15(5):319–37. pmid:16416750
  21. 21. van den Berg M, van Poppel M, van Kamp I, Andrusaityte S, Balseviciene B, Cirach M, et al. Visiting green space is associated with mental health and vitality: A cross-sectional study in four European cities. Health & Place. 2016;38:8–15. http://dx.doi.org/10.1016/j.healthplace.2016.01.003.
  22. 22. Taylor L, Hochuli DF. Defining greenspace: Multiple uses across multiple disciplines. Landscape and Urban Planning. 2017;158:25–38. https://doi.org/10.1016/j.landurbplan.2016.09.024.
  23. 23. Alcock I, White MP, Wheeler BW, Fleming LE, Depledge MH. Longitudinal effects on mental health of moving to greener and less green urban areas. Environmental science & technology. 2014;48(2):1247–55. Epub 2013/12/11. pmid:24320055.
  24. 24. White MP, Alcock I, Wheeler BW, Depledge MH. Would you be happier living in a greener urban area? A fixed-effects analysis of panel data. Psychological Science. 2013;24(6):920–8. http://dx.doi.org/10.1177/0956797612464659.
  25. 25. White MP, Alcock I, Wheeler BW, Depledge MH. Coastal proximity, health and well-being: results from a longitudinal panel survey. Health & place. 2013;23:97–103.
  26. 26. Henderson LW, Knight T. Integrating the hedonic and eudaimonic perspectives to more comprehensively understand wellbeing and pathways to wellbeing. International Journal of Wellbeing. 2012;2(3).
  27. 27. Ryan RM, Deci EL. On happiness and human potentials: A review of research on hedonic and eudaimonic well-being. Annual review of psychology. 2001;52(1):141–66.
  28. 28. Cassiers I. Beyond GDP, Measuring progress, true wealth, and the well-being of nations: Conference Proceedings. 2009:15, 97, 180, 1, 91, 93.
  29. 29. De Neve J-E, Oswald AJ. Estimating the influence of life satisfaction and positive affect on later income using sibling fixed effects. Proceedings of the National Academy of Sciences. 2012;109(49):19953–8.
  30. 30. Oswald AJ, Proto E, Sgroi D. Happiness and productivity. Journal of Labor Economics. 2015;33(4):789–822.
  31. 31. Gascon M, Triguero-Mas M, Martínez D, Dadvand P, Forns J, Plasència A, et al. Mental health benefits of long-term exposure to residential green and blue spaces: a systematic review. International journal of environmental research and public health. 2015;12(4):4354–79. pmid:25913182
  32. 32. Higgins JP, Green S. Cochrane handbook for systematic reviews of interventions: John Wiley & Sons; 2011.
  33. 33. Khan KS, Ter Riet G, Glanville J, Sowden AJ, Kleijnen J. Undertaking systematic reviews of research on effectiveness: CRD’s guidance for carrying out or commissioning reviews: NHS Centre for Reviews and Dissemination; 2001.
  34. 34. Higgins JP, Altman DG, Gøtzsche PC, Jüni P, Moher D, Oxman AD, et al. The Cochrane Collaboration’s tool for assessing risk of bias in randomised trials. Bmj. 2011;343:d5928. pmid:22008217
  35. 35. Wells G, Shea B, O’connell D, Peterson J, Welch V, Losos M, et al. The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses. Ottawa: Ottawa Hospital Research Institute; 2011. oxford. asp; 2011.
  36. 36. McPheeters ML, Kripalani S, Peterson NB, Idowu RT, Jerome RN, Potter SA, et al. Closing the quality gap: revisiting the state of the science (vol. 3: quality improvement interventions to address health disparities). Evidence report/technology assessment. 2012;(2083):1.
  37. 37. Hawker S, Payne S, Kerr C, Hardey M, Powell J. Appraising the evidence: reviewing disparate data systematically. Qualitative Health Research. 2002;12(9):1284–99. pmid:12448672
  38. 38. Alcock I, White MP, Lovell R, Higgins SL, Osborne NJ, Husk K, et al. What accounts for ‘England’s green and pleasant land'? A panel data analysis of mental health and land cover types in rural England. Landscape and Urban Planning. 2015;142:38–46.
  39. 39. Ambrey C, Fleming C. Public Greenspace and Life Satisfaction in Urban Australia. Urban Studies. 2014;51(6):1290–321.
  40. 40. Ambrey CL. Urban greenspace, physical activity and wellbeing: The moderating role of perceptions of neighbourhood affability and incivility. Land Use Policy. 2016;57:638–44.
  41. 41. Ambrey CL. An investigation into the synergistic wellbeing benefits of greenspace and physical activity: Moving beyond the mean. Urban Forestry and Urban Greening. 2016;19:7–12.
  42. 42. Ambrey C. Greenspace, physical activity and well-being in Australian capital cities: how does population size moderate the relationship? Public health. 2016;133:38–44. pmid:26715318
  43. 43. Bos EH, van der Meulen L, Wichers M, Jeronimus BF. A Primrose Path? Moderating Effects of Age and Gender in the Association between Green Space and Mental Health. International Journal of Environmental Research and Public Health. 2016;13(5). pmid:27187428
  44. 44. de Vries S, Van Dillen SM, Groenewegen PP, Spreeuwenberg P. Streetscape greenery and health: stress, social cohesion and physical activity as mediators. Social Science & Medicine. 2013;94:26–33.
  45. 45. Dzhambov A, Hartig T, Markevych I, Tilov B, Dimitrova D. Urban residential greenspace and mental health in youth: different approaches to testing multiple pathways yield different conclusions. Environmental research. 2018;160:47–59. pmid:28961469
  46. 46. Houlden V, Weich S, Jarvis S. A cross-sectional analysis of green space prevalence and mental wellbeing in England. BMC public health. 2017;17(1):460. pmid:28693451
  47. 47. Maas J, Van Dillen SM, Verheij RA, Groenewegen PP. Social contacts as a possible mechanism behind the relation between green space and health. Health & place. 2009;15(2):586–95.
  48. 48. Taylor L, Hahs AK, Hochuli DF. Wellbeing and urban living: nurtured by nature. Urban Ecosystems. 2018;21(1):197–208.
  49. 49. Triguero-Mas M, Dadvand P, Cirach M, Martínez D, Medina A, Mompart A, et al. Natural outdoor environments and mental and physical health: relationships and mechanisms. Environment international. 2015;77:35–41. pmid:25638643
  50. 50. Triguero-Mas M, Donaire-Gonzalez D, Seto E, Valentín A, Martínez D, Smith G, et al. Natural outdoor environments and mental health: Stress as a possible mechanism. Environmental research. 2017;159:629–38. pmid:28938204
  51. 51. Vemuri AW, Costanza R. The role of human, social, built, and natural capital in explaining life satisfaction at the country level: Toward a National Well-Being Index (NWI). Ecological Economics. 2006;58(1):119–33.
  52. 52. Ward Thompson C, Aspinall P, Roe J. Access to Green Space in Disadvantaged Urban Communities: Evidence of salutogenic effects based on biomarker and self-report measures of wellbeing. In: Abbas MY, editor. Amer International Conference on Quality of Life, Aicqol2014. Procedia Social and Behavioral Sciences. 1532014. p. 10–22.
  53. 53. Wood L, Hooper P, Foster S, Bull F. Public green spaces and positive mental health–investigating the relationship between access, quantity and types of parks and mental wellbeing. Health & place. 2017;48:63–71.
  54. 54. Annerstedt M, Ostergren PO, Bjork J, Grahn P, Skarback E, Wahrborg P. Green qualities in the neighbourhood and mental health-results from a longitudinal cohort study in Southern Sweden. European Journal of Public Health. 2012;22:275–6.
  55. 55. Luck GW, Davidson P, Boxall D, Smallbone L. Relations between urban bird and plant communities and human well-being and connection to nature. Conservation biology: the journal of the Society for Conservation Biology. 2011;25(4):816–26. Epub 2011/05/04. pmid:21535147.
  56. 56. MacKerron G, Mourato S. Happiness is greater in natural environments. Global Environmental Change. 2013;23(5):992–1000.
  57. 57. Sugiyama T, Leslie E, Giles-Corti B, Owen N. Associations of neighbourhood greenness with physical and mental health: do walking, social coherence and local social interaction explain the relationships? Journal of epidemiology and community health. 2008;62(5):e9. Epub 2008/04/24. pmid:18431834.
  58. 58. van den Bosch MA, Ostergren PO, Grahn P, Skarback E, Wahrborg P. Moving to Serene Nature May Prevent Poor Mental Health—Results from a Swedish Longitudinal Cohort Study. International journal of environmental research and public health. 2015;12(7):7974–89. Epub 2015/07/18. pmid:26184268
  59. 59. Vemuri AW, Grove JM, Wilson MA, Burch WR, Jr. A Tale of Two Scales: Evaluating the Relationship among Life Satisfaction, Social Capital, Income, and the Natural Environment at Individual and Neighborhood Levels in Metropolitan Baltimore. Environment & Behavior. 2011;43(1):3–25. http://dx.doi.org/10.1177/0013916509338551.
  60. 60. Weimann H, Rylander L, Albin M, Skärbäck E, Grahn P, Östergren P-O, et al. Effects of changing exposure to neighbourhood greenness on general and mental health: A longitudinal study. Health & Place. 2015;33:48–56. http://dx.doi.org/10.1016/j.healthplace.2015.02.003.
  61. 61. Gilchrist K, Brown C, Montarzino A. Workplace settings and wellbeing: Greenspace use and views contribute to employee wellbeing at pen-urban business sites. Landscape and Urban Planning. 2015;138:32–40.
  62. 62. Duvall J, Kaplan R. Enhancing the well-being of veterans using extended group-based nature recreation experiences. Journal of rehabilitation research and development. 2014;51(5):685–96. Epub 2014/12/17. pmid:25509055
  63. 63. Herzog TR, Strevey SJ. Contact with nature, sense of humor, and psychological well-being. Environment and Behavior. 2008;40(6):747–76.
  64. 64. Jakubec SL, Carruthers Den Hoed D, Ray HK, Ashok . Mental well-being and quality-of-life benefits of inclusion in nature for adults with disabilities and their caregivers. Landscape Research. 2016:1–12.
  65. 65. Kamitsis I, Francis AJ. Spirituality mediates the relationship between engagement with nature and psychological wellbeing. Journal of Environmental Psychology. 2013;36:136–43.
  66. 66. Marselle MR, Irvine KN, Warber SL. Walking for well-being: are group walks in certain types of natural environments better for well-being than group walks in urban environments? International journal of environmental research and public health. 2013;10(11):5603–28. Epub 2013/11/01. pmid:24173142
  67. 67. Marselle MR, Irvine KN, Lorenzo-Arribas A, Warber SL. Moving beyond green: exploring the relationship of environment type and indicators of perceived environmental quality on emotional well-being following group walks. International journal of environmental research and public health. 2015;12(1):106–30. Epub 2014/12/30. pmid:25546275
  68. 68. Molsher R, Townsend M. Improving Wellbeing and Environmental Stewardship Through Volunteering in Nature. Ecohealth. 2016;13(1):151–5. pmid:26678275
  69. 69. Nisbet EK, Zelenski JM. Underestimating nearby nature: Affective forecasting errors obscure the happy path to sustainability. Psychological Science. 2011;22(9):1101–6. http://dx.doi.org/10.1177/0956797611418527.
  70. 70. Panno A, Carrus G, Lafortezza R, Mariani L, Sanesi G. Nature-based solutions to promote human resilience and wellbeing in cities during increasingly hot summers. Environmental research. 2017;159:249–56. pmid:28822309
  71. 71. Richardson M, Cormack A, McRobert L, Underhill R. 30 Days Wild: Development and Evaluation of a Large-Scale Nature Engagement Campaign to Improve Well-Being. PloS one. 2016;11(2):e0149777. pmid:26890891
  72. 72. White MP, Pahl S, Wheeler BW, Depledge MH, Fleming LE. Natural environments and subjective wellbeing: Different types of exposure are associated with different aspects of wellbeing. Health & place. 2017;45:77–84.
  73. 73. Dadvand P, Bartoll X, Basagaña X, Dalmau-Bueno A, Martinez D, Ambros A, et al. Green spaces and general health: roles of mental health status, social support, and physical activity. Environment international. 2016;91:161–7. pmid:26949869
  74. 74. Krekel C, Kolbe J, Wüstemann H. The Greener, the Happier? The Effects of Urban Green and Abandoned Areas on Residential Well-Being. The Effects of Urban Green and Abandoned Areas on Residential Well-Being (January 2015) SOEPpaper. 2015;(728).
  75. 75. Cervinka R, Röderer K, Hefler E. Are nature lovers happy? On various indicators of well-being and connectedness with nature. Journal of Health Psychology. 2012;17(3):379–88. http://dx.doi.org/10.1177/1359105311416873.
  76. 76. Howell AJ, Dopko RL, Passmore H-A, Buro K. Nature connectedness: Associations with well-being and mindfulness. Personality and Individual Differences. 2011;51(2):166–71.
  77. 77. Howell AJ, Passmore H-A, Buro K. Meaning in nature: meaning in life as a mediator of the relationship between nature connectedness and well-being. Journal of Happiness Studies. 2013;14(6):1681–96.
  78. 78. Nisbet EK, Zelenski JM, Murphy SA. Happiness is in our nature: Exploring nature relatedness as a contributor to subjective well-being. Journal of Happiness Studies. 2011;12(2):303–22. http://dx.doi.org/10.1007/s10902-010-9197-7.
  79. 79. Zelenski JM, Nisbet EK. Happiness and Feeling Connected: The Distinct Role of Nature Relatedness. Environment and Behavior. 2014;46(1):3–23. http://dx.doi.org/10.1177/0013916512451901.
  80. 80. Zhang JW, Howell RT, Iyer R. Engagement with natural beauty moderates the positive relation between connectedness with nature and psychological well-being. Journal of Environmental Psychology. 2014;38:55–63.
  81. 81. Tennant R, Hiller L, Fishwick R, Platt S, Joseph S, Weich S, et al. The Warwick-Edinburgh mental well-being scale (WEMWBS): development and UK validation. Health and Quality of life Outcomes. 2007;5(1):1.
  82. 82. Guðmundsdóttir D, editor The short Warwick-Edinburgh mental well-being scale (SWEMWBS): Internal validity and the relationship between SWEMWBS, age, gender and other health and well-being measures. 2nd Applied Positive Psychology Conference, Warwick; 2009.
  83. 83. Office for National Statistics. Personal Wellbeing User Guidance Online2016 [cited 2018 21st January]. https://www.ons.gov.uk/peoplepopulationandcommunity/wellbeing/methodologies/personalwellbeingsurveyuserguide.
  84. 84. Psychiatric Research Unit. WHO (Five) Well-Being Index (1998 version). WHO Collaborating Centre in Mental Health. 1998.
  85. 85. World Health Organization. WHOQOL-BREF: introduction, administration, scoring and generic version of the assessment: field trial version, December 1996. 1996.
  86. 86. Ware JE, Kosinski M, Dewey JE, Gandek B. SF-36 health survey: manual and interpretation guide: Quality Metric Inc.; 2000.
  87. 87. Self A, Thomas J, Randall C. Measuring national well-being: life in the UK, 2012. Newport: UK Office for National Statistics. 2012.
  88. 88. Organisation for Economic Co-operation and Development. OECD guidelines on measuring subjective well-being 2013.
  89. 89. Cimprich B. Development of an intervention to restore attention in cancer patients. Cancer nursing. 1993;16(2):83–92. pmid:8477404
  90. 90. Watson D, Clark LA, Tellegen A. Development and validation of brief measures of positive and negative affect: the PANAS scales. Journal of personality and social psychology. 1988;54(6):1063. pmid:3397865
  91. 91. McNair DM, Lorr M, Droppleman LF. Profile of mood states: Educational and Industrial Testing Service San Diego, CA; 1981.
  92. 92. Hu Y, Stewart-Brown S, Twigg L, Weich S. Can the 12-item General Health Questionnaire be used to measure positive mental health? Psychological medicine. 2007;37(07):1005–13.
  93. 93. Ryff CD, Keyes CLM. The structure of psychological well-being revisited. Journal of personality and social psychology. 1995;69(4):719. pmid:7473027
  94. 94. Tarzia V. European Common Indicators: towards a local sustainability profile. Ambiente Italia Research Institute, Milano, Italy. 2003.
  95. 95. Ulrich RS. Human responses to vegetation and landscapes. Landscape and urban planning. 1986;13:29–44.
  96. 96. Coombes E, Jones AP, Hillsdon M. The relationship of physical activity and overweight to objectively measured green space accessibility and use. Social Science & Medicine. 2010;70(6):816–22. https://doi.org/10.1016/j.socscimed.2009.11.020.
  97. 97. Green Flag Award. What is the Green Flag Award Online: Department for Communities and Local Government; 2017 [cited 2017 18th December]. http://www.greenflagaward.org.uk/about-us/what-is-the-green-flag-award/.
  98. 98. Fone DL, Dunstan F. Mental health, places and people: a multilevel analysis of economic inactivity and social deprivation. Health & place. 2006;12(3):332–44.